Shovel

ABSTRACT

A shovel includes a turning drive unit. The turning drive unit includes a turning electric motor, a turning speed reducer configured to transmit the rotational driving force of the turning electric motor to a turnable body, a brake unit configured to maintain the turnable body in a state where the turning of the turnable body is stopped, and a case forming a space in which the turning speed reducer and the brake unit are lubricated with lubricant oil and accommodated. A recess is formed in part of the case that forms a bottom surface of the space.

CROSS-REFERENCE TO RELATED APPLICATION

This application is based upon and claims the benefit of priority ofJapanese Patent Application No. 2013-074943, filed on Mar. 29, 2013, theentire contents of which are incorporated herein by reference.

BACKGROUND

1. Technical Field

The present invention generally relates to shovels including a turningspeed reducer.

2. Description of Related Art

A related-art shovel is known that includes a turning mechanismincluding a turning electric motor, a first turning speed reducerconnected to the output shaft of the turning electric motor, a secondturning speed reducer connected to the output shaft of the first turningspeed reducer, a third turning speed reducer connected to the outputshaft of the second turning speed reducer, and a swing circle connectedto the output shaft of the third turning speed reducer.

SUMMARY

According to an aspect of the present invention, a shovel includes aturning drive unit. The turning drive unit includes a turning electricmotor, a turning speed reducer configured to transmit the rotationaldriving force of the turning electric motor to a turnable body, a brakeunit configured to maintain the turnable body in a state where theturning of the turnable body is stopped, and a case forming a space inwhich the turning speed reducer and the brake unit are lubricated withlubricant oil and accommodated. A recess is formed in part of the casethat forms a bottom surface of the space.

It is to be understood that both the foregoing general description andthe following detailed description are exemplary and explanatory and notrestrictive of the invention.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a side view of a shovel in which a turning drive unitaccording to an embodiment of the present invention is incorporated;

FIG. 2 is a block diagram illustrating a configuration of a drive systemof the shovel illustrated in FIG. 1;

FIG. 3 is a block diagram illustrating a configuration of a turningdrive unit according to an embodiment of the present invention;

FIG. 4 is a plan view of the turning drive unit of FIG. 3;

FIG. 5 is a cross-sectional view of the turning drive unit, taken alongthe line V-V of FIG. 4;

FIG. 6 is a cross-sectional view of the turning drive unit, taken alongthe line VI-VI of FIG. 4, illustrating a state of the turning drive unitat the time when an output shaft of a turning electric motor isstationary;

FIGS. 7A, 7B and 7C are detail views of a planetary carrier of a firstturning speed reducer;

FIG. 8 is a front view of an eyebolt used for disassembling andreassembling the planetary carrier;

FIG. 9 is an enlarged view of a region IX enclosed by a broken line inFIG. 6;

FIGS. 10A, 10B and 10C are cross-sectional views of part of a secondgear case;

FIG. 11 illustrates cross-sectional views illustrating the positionalrelationship between the planetary carrier and the second gear case; and

FIG. 12 illustrates cross-sectional views illustrating the positionalrelationship between the planetary carrier and the second gear case.

DETAILED DESCRIPTION

As mentioned above, for example, a related-art shovel includes a turningmechanism including a turning electric motor, a first turning speedreducer connected to the output shaft of the turning electric motor, asecond turning speed reducer connected to the output shaft of the firstturning speed reducer, a third turning speed reducer connected to theoutput shaft of the second turning speed reducer, and a swing circleconnected to the output shaft of the third turning speed reducer.

According to the related-art shovel, however, no measures are takenagainst the wear debris of components such as gears and a brake unit,generated during a turning operation.

According to an aspect of the invention, a shovel includes a turningdrive unit capable of efficiently discharging wear debris generatedduring a turning operation.

First, a description is given of an overall configuration and a drivesystem configuration of a shovel in which a turning drive unit accordingto an embodiment of the present invention is incorporated. FIG. 1 is aside view of a shovel in which a turning drive unit according to anembodiment of the present invention is incorporated. The shovel is anexample of a construction machine, and a turning drive unit according toan embodiment of the present invention may be incorporated into aconstruction machine that includes a mechanism for turning a turningbody.

Referring to FIG. 1, an upper-part turning body 3 (an upper-partturnable body) is mounted through a turning mechanism 2 on a lower-parttraveling body 1 (a lower-part movable body) of the shovel. A boom 4 isattached to the upper-part turning body 3. An arm 5 is attached to anend of the boom 4. A bucket 6 is attached to an end of the arm 5. Theboom 4, the arm 5, and the bucket 6 are hydraulically driven by a boomcylinder 7, an arm cylinder 8, and a bucket cylinder 9, respectively.Furthermore, a cabin 10 and power sources such as an engine are mountedon the upper-part turning body 3.

The shovel illustrated in FIG. 1 includes an electrical energy storageunit that stores electric power to be supplied to the turning driveunit. Embodiments of the present invention, however, may be applied toany shovel, even to, for example, an electrically driven shovel suppliedwith charging electric power from an external power supply, as long asthe shovel adopts electric turning.

FIG. 2 is a block diagram illustrating a configuration of a drive systemof the shovel illustrated in FIG. 1. In FIG. 2, a mechanical powersystem, a high-pressure hydraulic line, a pilot line, and an electricdrive and control system are indicated by a double line, a bold solidline, a broken line, and a fine solid line, respectively.

An engine 11 as a mechanical drive part and a motor generator 12 as anassist drive part are connected to a first input shaft and a secondinput shaft, respectively, of a transmission 13. A main pump 14 and apilot pump 15 are connected to the output shaft of the transmission 13as hydraulic pumps. A control valve 17 is connected to the main pump 14via a high-pressure hydraulic line 16. Furthermore, an operationapparatus 26 is connected to the pilot pump 15 via a pilot line 25.

The control valve 17 is a control unit that controls a hydraulic systemin the hybrid shovel. Hydraulic motors 1A (right) and 1B (left) for thelower-part traveling body 1, the boom cylinder 7, the arm cylinder 8,and the bucket cylinder 9, are connected to the control valve 17 viahigh-pressure hydraulic lines.

An electrical energy storage system (an electrical energy storage unit)120 including a capacitor as an electrical energy storage device isconnected to the motor generator 12 via an inverter 18. A turningelectric motor 21 as an electric work element is connected to theelectrical energy storage system 120 via an inverter 20. A resolver 22and a turning speed reducer 24 are connected to an output shaft 21 b ofthe turning electric motor 21. A mechanical brake 23 is connected to anoutput shaft 24A of the turning speed reducer 24. The turning electricmotor 21, the resolver 22, the mechanical brake 23, and the turningspeed reducer 24 form a turning drive unit 40 as a load drive system.Here, the turning electric motor 21 corresponds to a turning electricmotor for turning the upper-part turning body 3, and the mechanicalbrake 23 corresponds to a brake unit that mechanically brakes theupper-part turning body 3 in order to maintain the upper-part turningbody 3 in a state where turning is stopped.

The operation apparatus 26 includes a lever 26A, a lever 26B, and apedal 26C. The lever 26A, the lever 26B, and the pedal 26C are connectedto the control valve 17 and a pressure sensor 29 via a hydraulic line 27and a hydraulic line 28, respectively. The pressure sensor 29 isconnected to a controller 30 that controls driving of an electricsystem.

The controller 30 is a control unit serving as a main control part thatcontrols driving of the hybrid shovel. The controller 30 includes aprocessor including a CPU (Central Processing Unit) and an internalmemory. The controller 30 is a unit that is implemented by the CPUexecuting a drive control program contained in the internal memory.

The controller 30 converts a signal fed from the pressure sensor 29 intoa speed command, and controls driving of the turning electric motor 21.The signal fed from the pressure sensor 29 corresponds to a signal thatrepresents the amount of operation in the case of operating theoperation apparatus 26 in order to cause the turning mechanism 2 toturn.

The controller 30 controls the operation (switches the electric motor[assist] operation and the generator operation) of the motor generator12, and controls the charge and discharge of the capacitor bycontrolling driving of a step-up/step-down converter of the electricalenergy storage system 120. The controller 30 controls the charge anddischarge of the capacitor by controlling the switching of the step-upoperation and the step-down operation of the step-up/step-down converterof the electrical energy storage system 120 based on the state of chargeof the capacitor, the operating state (electric motor [assist] operationor generator operation) of the motor generator 12, and the operatingstate (power running operation or regenerative operation) of the turningelectric motor 21. Furthermore, the controller 30 also controls theamount of charging the capacitor (charging current or charging electricpower) as described below.

In the work performed by the shovel of the above-describedconfiguration, the turning electric motor 21 is driven with electricpower supplied via the inverter 20 in order to cause the upper-partturning body 3 to turn. The rotational force of the output shaft 21 b ofthe turning electric motor 21 is transmitted to an output shaft 40A ofthe turning drive unit 40 via the turning speed reducer 24 and themechanical brake 23.

FIG. 3 is a block diagram illustrating a configuration of the turningdrive unit 40 according to an embodiment of the present invention. Asdescribed above, the turning drive unit 40 includes the turning electricmotor 21, which is an electric motor serving as a drive source. Theturning speed reducer 24 is connected to the output shaft side of theturning electric motor 21.

Specifically, the turning speed reducer 24 includes the three-stageconfiguration of a first turning speed reducer 24-1, a second turningspeed reducer 24-2, and a third turning speed reducer 24-3. Each of thefirst turning speed reducer 24-1, the second turning speed reducer 24-2,and the third turning speed reducer 24-3 includes a planetary speedreducer. To be more specific, the first turning speed reducer 24-1 atthe first stage is attached to the turning electric motor 21.Furthermore, a disk brake serving as the mechanical brake 23 is providedon a planetary carrier 46 (FIG. 5) that serves as the output shaft ofthe first turning speed reducer 24-1. Furthermore, the second turningspeed reducer 24-2 at the second stage is attached to the first turningspeed reducer 24-1 with the mechanical brake 23 being interposed betweenthe first turning speed reducer 24-1 and the second turning speedreducer 24-2, and the third turning speed reducer 24-3 at the thirdstage is attached to the second turning speed reducer 24-2. The outputshaft of the third turning speed reducer 24-3 serves as the output shaft40A of the turning drive unit 40. Although not graphically represented,the output shaft 40A of the turning drive unit 40 is connected to theturning mechanism 2, so that the turning mechanism 2 is driven by therotational force of the output shaft 40A.

Next, a description is given, with reference to FIG. 4 and FIG. 5, of aspecific configuration of the turning drive unit 40. FIG. 4 is a planview of the turning drive unit 40. In FIG. 4, broken lines indicate thehidden outlines of components of the first turning speed reducer 24-1.Furthermore, FIG. 5 is a cross-sectional view of the turning drive unit40, taken along the line V-V of FIG. 4.

Furthermore, FIG. 5 is a cross-sectional view of part of the turningdrive unit 40 that forms the first turning speed reducer 24-1 and themechanical brake 23. In this embodiment, a sun gear 42 of a planetaryspeed reducer forming the first turning speed reducer 24-1 is fixed tothe output shaft 21 b of the turning electric motor 21. Furthermore, thesun gear 42 is rotatably supported by the planetary carrier 46 via abearing 51. Furthermore, the sun gear 42 meshes with each of threeplanetary gears 44. Each of the planetary gears 44 is rotatablysupported via a pin 44 a on the planetary carrier 46 forming the outputshaft of the first turning speed reducer 24-1. Each of the planetarygears 44 meshes with an internal gear 48 formed on the interior surfaceof a first gear case 50.

The first gear case 50, on which the internal gear 48 is formed, isfixed to an end plate 21 a of the turning electric motor 21 so as to beprevented from rotating. On the other hand, the planetary carrier 46,which forms the output shaft of the first turning speed reducer 24-1, issupported via a bearing 56 so as to be rotatable relative to a secondgear case 52 fixed to the first gear case 50.

The above-described first turning speed reducer 24-1 has a structuresuch that lubricant oil for lubricating gears is hermetically sealed inby the end plate 21 a and the output shaft 21 b of the turning electricmotor 21, the first gear case 50, the second gear case 52, and theplanetary carrier 46.

In the first turning speed reducer 24-1 of the above-describedconfiguration, when the output shaft 21 b of the turning electric motor21 rotates to cause the sun gear 42 to rotate, the planetary gears 44rotate. The planetary gears 44 mesh with the internal gear 48 formed onthe interior surface of the first gear case 50. Therefore, a force in adirection to cause the first gear case 50, on which the internal gear 48is formed, to rotate, is applied by the rotational force of theplanetary gears 44. The first gear case 50, however, is fixed to the endplate 21 a of the turning electric motor 21 so as to be prevented fromrotating. As a result, the planetary carrier 46, which is rotatablysupported while supporting the planetary gears 44, rotates. By the gearaction as described above, the rotational speed of the output shaft 21 bof the turning electric motor 21 is reduced and output from theplanetary carrier 46.

Next, a description is given of a structure of a disk brake that formsthe mechanical brake 23. The disk brake is formed between the secondgear case 52, which is a stationary part, and the planetary carrier 46,which is an output shaft. Brake disks 60 extend outward in a directionof a radius of rotation from the periphery of the planetary carrier 46.The brake disks 60 are connected to the planetary carrier 46 via aconnecting structure such as a spline connection so as to be preventedfrom rotating relative to the planetary carrier 46 but movable in theaxial directions of the planetary carrier 46.

A brake plate 62 is placed on each of the upper side and the lower sideof each of the brake disks 60. The brake plates 62 are connected to theinterior surface of the second gear case 52 via a connecting structuresuch as a spline connection so as to be prevented from rotating relativeto the second gear case 52, which is a stationary part, but movable inthe axial directions of the planetary carrier 46. This embodiment adoptsa configuration where each of the two brake disks 60 is held betweencorresponding two of the three brake plates 62. Embodiments of thepresent invention, however, are not limited to this configuration. Forexample, a single brake disk 60 may alternatively be held between twobrake plates 62 or each of three or more brake disks 60 mayalternatively be held between corresponding two of four or more brakeplates 62.

A piston 64 is placed on a topmost one of the brake plates 62 so as tobe movable in the axial directions of the planetary carrier 46. Thepiston 64 is pressed against the topmost one of the brake plates 62 bysprings 66. According to this embodiment, coil springs are used as thesprings 66. Alternatively, it is also possible to use Belleville washersstacked on top of each other in multiple tiers, which may produce highoutput with a small deflection.

The brake plates 62 and the brake disks 60 are movable in the axialdirections of the planetary carrier 46. Therefore, when the topmost oneof the brake plates 62 is pressed by the piston 64, each of the brakedisks 60 is held and pressed between corresponding upper and lower onesof the brake plates 62. The surfaces of the brake plates 62 and thebrake disks 60 are covered with a coating of a high coefficient offriction. Each of the brake disks 60 is held and pressed betweencorresponding two of the brake plates 62, so that a brake force toprevent the rotations of the brake disks 60 acts on the brake disks 60.Furthermore, the brake disks 60 are connected to the planetary carrier46 in a non-rotatable manner. Therefore, the brake force that acts onthe brake disks 60 serves as a brake force applied to the planetarycarrier 46.

A hydraulic space 68 into which hydraulic fluid is suppliable is formedbetween the piston 64 and the second gear case 52. A brake release port69 is connected to the hydraulic space 68. Furthermore, sealing members91 such as O-rings are placed between the piston 64 and the second gearcase 52 so as to seal the hydraulic space 68 to prevent a leakage ofhydraulic fluid from the hydraulic space 68. When a hydraulic pressureis supplied from the pilot pump 15 to the hydraulic space 68 via theoperation apparatus 26, a hydraulic line 27 a (FIG. 2), and the brakerelease port 69, the piston 64 is pressed upward by the hydraulicpressure, so that a force to press the brake plates 62 is lost. As aresult, the brake is released.

According to this embodiment, in the first turning speed reducer 24-1 ofthe above-described configuration, an annular recess is formed on anupper surface of the first gear case 50, and multiple through holes areformed at the bottom of the annular recess. The springs 66 are insertedin the corresponding through holes. Respective lower ends of the springs66 project from the corresponding through holes of the first gear case50 to be in contact with the bottom surfaces of corresponding holesformed in the piston 64. A spring holding member 90 is fitted in theannular recess of the first gear case 50. The spring holding member 90is fastened and fixed to the first gear case 50 by multiple bolts 92.

Before the spring holding member 90 is fixed to the first gear case 50in the annular recess, respective upper ends of the springs 66 areprojecting upward from the bottom surface of the annular recess.Accordingly, at the time of fixing the spring holding member 90 to thefirst gear case 50 in the annular recess, the springs 66 are pressed andcompressed by the spring holding member 90.

With the spring holding member 90 being fixed to the first gear case 50in the annular recess, the springs 66 are held and compressed betweenthe spring holding member 90 and the piston 64. The resilience (springforce) of each of the springs 66 at this point serves as a force topress the piston 64 (that is, the brake plates 62) against the brakedisks 60, and becomes a brake force applied to the planetary carrier 46.

With the spring holding member 90 being fixed to the first gear case 50in the annular recess, the entire spring holding member 90 isaccommodated inside the annular recess. Therefore, the spring holdingmember 90 is prevented from projecting from a matching surface of thefirst gear case 50 which surface comes into contact with the end plate21 a (which may also be called “flange”) of the turning electric motor21. Accordingly, the matching surface of the first gear case 50 alonecomes into contact with the end plate 21 a of the turning electric motor21. On an upper surface of the spring holding member 90, however, asealing member 93 such as an O-ring is placed to provide sealing toprevent lubricant oil that lubricates and cools the planetary gears 44inside the first gear case 50 from leaking out.

Furthermore, a sealing member 94 such as an O-ring is placed on a lowersurface of the spring holding member 90 to provide sealing to preventlubricant oil filling in a part where the springs 66 are accommodatedfrom leaking out. Likewise, a sealing member 95 such as an O-ring isplaced between the first gear case 50 and the second gear case 52 toprovide sealing to prevent lubricant oil filling in the part where thesprings 66 are accommodated from leaking out.

Next, a description is given, with reference to FIG. 6, of transmissionof a rotational driving force in the turning drive unit 40. FIG. 6 is across-sectional view of the turning drive unit 40, taken along the lineVI-VI of FIG. 4, illustrating a state of the turning drive unit 40 atthe time when the output shaft 21 b of the turning electric motor 21 isstationary.

Referring to FIG. 6, the first turning speed reducer 24-1 includes aplanetary gear mechanism including the sun gear 42, the planetary gears44, the planetary carrier 46, and the internal gear 48. The secondturning speed reducer 24-2 includes a planetary gear mechanism includinga sun gear 82, planetary gears 84, a planetary carrier 86, and aninternal gear 88. Likewise, the third turning speed reducer 24-3includes a planetary gear mechanism including a sun gear 102, planetarygears 104, a planetary carrier 106, and an internal gear 108.

In the first turning speed reducer 24-1, the sun gear 42 is fixed to theoutput shaft 21 b of the turning electric motor 21 and meshes with theplanetary gears 44. The planetary gears 44 revolve around the sun gear42 between the sun gear 42 and the internal gear 48, formed on theinterior wall surface of the first gear case 50, while rotating.According to this embodiment, the first turning speed reducer 24-1includes the three planetary gears 44. Each of the three planetary gears44 causes the planetary carrier 46 to rotate by revolving around the sungear 42 while rotating. The planetary carrier 46 forms the output shaftof the first turning speed reducer 24-1.

In the second turning speed reducer 24-2, the sun gear 82 is fixed tothe planetary carrier 46 serving as the output shaft of the firstturning speed reducer 24-1, and meshes with the planetary gears 84. Theplanetary gears 84 revolve around the sun gear 82 between the sun gear82 and the internal gear 88, formed on the interior wall surface of athird gear case 54, while rotating. According to this embodiment, thesecond turning speed reducer 24-2 includes the three planetary gears 84.Each of the three planetary gears 84 is rotatably supported on theplanetary carrier 86 through a corresponding one of pins 84 a, andcauses the planetary carrier 86 to rotate by revolving around the sungear 82 while rotating. The planetary carrier 86 forms the output shaftof the second turning speed reducer 24-2.

In the third turning speed reducer 24-3, the sun gear 102 is fixed tothe planetary carrier 86 serving as the output shaft of the secondturning speed reducer 24-2, and meshes with the planetary gears 104. Theplanetary gears 104 revolve around the sun gear 102 between the sun gear102 and the internal gear 108, formed on the interior wall surface ofthe third gear case 54, while rotating. According to this embodiment,the third turning speed reducer 24-3 includes the three planetary gears104. Each of the three planetary gears 104 is rotatably supported on theplanetary carrier 106 through a corresponding one of pins 104 a, andcauses the planetary carrier 106 to rotate by revolving around the sungear 102 while rotating. The planetary carrier 106 forms the outputshaft 40A of the turning speed reducer 24.

By the above-described configuration, the turning drive unit 40 reducesthe rotational speed of the output shaft 21 a of the turning electricmotor 21 and increases the torque of the output shaft 40A.

Specifically, the turning drive unit 40 causes the planetary carrier 46to rotate clockwise by causing the planetary gears 44, in accordancewith the high-speed, low-torque clockwise rotation of the output shaft21 b, to revolve clockwise around the sun gear 42 while rotatingcounterclockwise. Then, the turning drive unit 40 causes the planetarycarrier 86 to rotate clockwise by causing the planetary gears 84, inaccordance with the clockwise rotation of the planetary carrier 46, torevolve clockwise around the sun gear 82 while rotatingcounterclockwise. Furthermore, the turning drive unit 40 causes theplanetary carrier 106, that is, the output shaft 40A, to rotateclockwise at low speed with high torque by causing the planetary gears104, in accordance with the clockwise rotation of the planetary carrier86, to revolve clockwise around the sun gear 102 while rotatingcounterclockwise. In the case where the output shaft 21 b rotatescounterclockwise, the turning drive unit 40 operates in the same mannerexcept that each gear rotates in the reverse direction.

Furthermore, the turning drive unit 40 includes a space SP1 hermeticallysealed by the output shaft 21 b, the end plate 21 a, the first gear case50, the second gear case 52, and the planetary carrier 46. An oil seal(not graphically represented) is attached to the output shaft 21 b.Furthermore, two oil seals 57 are attached to the planetary carrier 46below the bearing 56. The space SP1 accommodates the sun gear 42, theplanetary gears 44, the planetary carrier 46, the brake disks 60, thebrake plates 62, and the piston 64, which are lubricated by lubricantoil LB1, which is indicated by a fine dot pattern in FIG. 6.

Furthermore, the turning drive unit 40 includes a space SP2 hermeticallysealed by the planetary carrier 46, the second gear case 52, the thirdgear case 54, and the planetary carrier 106. An oil seal (notgraphically represented) is attached to the planetary carrier 106. Thespace SP2 accommodates the sun gears 82 and 102, the planetary gears 84and 104, and the planetary carriers 86 and 106, which are lubricated bylubricant oil LB2, which is indicated by a coarse dot pattern in FIG. 6.The lubricant LB2 is separated from the lubricant oil LB1 by the oilseals 57. Furthermore, the lubricant oil LB2 may be of either the samekind as or a different kind from the lubricant oil LB1. For example, inthe turning drive unit 40, the lubricant oil LB1 for high-speed rotationmay be different in kind from the lubricant oil LB2 for low-speedrotation.

Next, a description is given in detail, with reference to FIGS. 7A, 7Band 7C, of the planetary carrier 46, which serves as the output shaft ofthe first turning speed reducer 24-1. FIGS. 7A through 7C are detailviews of the planetary carrier 46. FIGS. 7A and 7B are a front view anda plan view, respectively, of the planetary carrier 46. FIG. 7C is across-sectional view of the planetary carrier 46, where a planeperpendicular to the plane of paper of FIG. 7B, indicated by a dot-dashline, is viewed in a direction indicated by arrows X.

As illustrated in FIGS. 7A through 7C, the planetary carrier 46 includesan output shaft part 46 a, which forms an output shaft, and a carrierpart 46 b, by which three planetary gears 44-1, 44-2, and 44-3 arerotatably held.

The output shaft part 46 a includes a radially extended disk portion 46a 1 and an axially elongated columnar portion 46 a 2.

At an outer radial end of the disk portion 46 al, the disk portion 46 a1 includes a disk holding portion 46 a 1 p that holds the brake disks60. According to this embodiment, the disk holding portion 46 a 1 pholds the two brake disks 60, and is thicker than other parts of thedisk portion 46 a 1 positioned radially inside the disk holding portion46 a 1 p. This configuration makes it possible to increase the stiffnessof the disk holding portion 46 a 1 p against a force received from thebrake disks 60 at the time of braking, compared with the case where thedisk holding portion 46 a 1 p have the same thickness (length in anaxial direction) as other parts of the disk portion 46 a 1. Furthermore,this also makes it possible to increase the number of brake disksattached to the disk holding portion 46 a 1 p.

The carrier part 46 b is a member detachable from and reattachable tothe output shaft part 46 b. According to this embodiment, the carrierpart 46 b is a columnar member that accommodates the sun gear 42, fixedto the output shaft 21 b of the turning electric motor 21, and the threeplanetary gears 44-1, 44-2 and 44-3. Furthermore, the carrier part 46 bis fastened to the output shaft part 46 a using three bolts 46 c-1, 46c-2 and 46 c-3 (hereinafter also collectively referred to as “bolts 46c”), which are fastening members. Furthermore, the planetary gears 44-1,44-2 and 44-3 (hereinafter also collectively referred to as “planetarygears 44”) are rotatably supported by the carrier part 46 b using threepins 44 a-1, 44 a-2 and 44 a-3 (hereinafter also collectively referredto as “pins 44 a”).

According to this embodiment, the three bolts 46 c are inserted intobolt holes formed in the carrier part 46 b at 120-degree intervalsaround its central axis.

The bolts 46 c are then screwed into tap holes (not graphicallyrepresented) formed on an upper surface of the disk portion 46 a 1 ofthe output shaft part 46 a to fasten the carrier part 46 b to the outputshaft part 46 a. Furthermore, the three pins 44 a are inserted into pinholes formed in the carrier part 46 b at 120-degree intervals around itscentral axis so as to alternate with the three bolts 46 c at 60-degreeintervals. The pins 44 a are then fixed with the corresponding planetarygears 44 being rotatably supported by the pins 44 a.

According to this embodiment, the respective central axes of the threebolts 46 c are positioned on the circumference of the same circle whosecenter coincides with the central axis of the carrier part 46 b.Furthermore, the respective central axes of the three pins 44 a arepositioned on the circumference of the same circle whose centercoincides with the central axis of the carrier part 46 b. The respectivecentral axes of the three bolts 46 c and the respective central axes ofthe three pins 44 a are positioned on the circumference of the samecircle whose center coincides with the central axis of the carrier part46 b. Embodiments of the present invention, however, are not limited tothis configuration. For example, the respective central axes of thethree bolts 46 c may alternatively pass through a circle different froma circle through which the respective central axes of the three pins 44a pass.

Furthermore, two tap holes 46 d-1 and 46 d-2 (hereinafter alsocollectively referred to as “tap holes 46 d”) for preventing the carrierpart 46 b and the output shaft part 46 a from rotating together whenfastening or loosening the three bolts 46 c serving as fastening membersare formed in the carrier part 46 b. According to this embodiment, thetwo tap holes 46 d are formed at positions symmetrical about the centralaxis of the carrier part 46 b.

Here, a description is given, with reference to FIGS. 7A through 7C andFIG. 8, of a method of removing the carrier part 46 b from the outputshaft part 46 a by, for example, a worker.

First, a worker attaches a jig such as an eyebolt as illustrated in FIG.8 to each of the two tap holes 46 d.

Thereafter, the worker passes a single bar-shaped member through therings of the eyebolts 80 attached to the two tap holes 46 d. Thebar-shaped member is, for example, a rigid member such as a crowbar.

Thereafter, while having the bar-shaped member fixed, the worker loosensthe bolts 46 c using a tool such as a wrench. The fixation of thebar-shaped member prevents the carrier part 46 b from rotating with theoutput shaft part 46 a when loosening the bolts 46 c.

The above description, which relates to the method of removing thecarrier part 46 b from the output shaft part 46 a by a worker, may alsobe applied to the case of attaching the carrier part 46 b to the outputshaft part 46 a by a worker.

As described above, the output shaft part 46 a is a unitary structure ofthe disk portion 46 a 1, to which the brake disks 60 are connected, andthe columnar portion 46 a 2, which is connected to the sun gear 82 ofthe second turning speed reducer 24-2. Therefore, no wear is causedbetween the disk portion 46 a 1 and the columnar portion 46 a 2.Furthermore, it is possible to increase the proof stress of the outputshaft part 46 a against a braking reaction force generated at the timeof braking by a brake unit.

Furthermore, the carrier part 46 b is connected to the output shaft part46 a using the bolts 46 c serving as fastening members, withoutemploying spline connection or serration connection. Therefore, it ispossible to reduce wear at connections.

Furthermore, the output shaft part 46 a and the carrier part 46 b, whichare separate independent members, may be manufactured of differentmaterials. Therefore, the output shaft part 46 a, which includes partsthat are likely to wear out, may be formed of a material having moreresistance to wear than the material of the carrier part 46 b. Parts ofthe output shaft part 46 a that are likely to wear out includes a partspline-connected to the sun gear 82 of the second turning speed reducer24-2 and a part spline-connected to the brake disks 60. On the otherhand, the carrier part 46 b, which is not required to have highresistance to wear, may be formed of a relatively low-cost material. Asa result, this structure of the planetary carrier 46 makes it possibleto prevent an increase in manufacturing costs while increasing the wearresistance of parts that are likely to wear out, compared with the caseof forming the output shaft part 46 a and the carrier part 46 b as aunitary structure. Furthermore, the increased wear resistance makes itpossible to extend the cycle of replacement of the output shaft part 46a and thus to reduce replacement costs. Furthermore, because the outputshaft part 46 a and the carrier part 46 b are separate independentmembers, there is no need to time the replacement of the carrier part 46b to coincide with the replacement of the output shaft part 46 a, whosecycle of replacement is relatively short. Furthermore, the output shaftpart 46 a may be replaced by simply separating the output shaft part 46a and the carrier part 46 b without removing the planetary gears 44 fromthe carrier part 46 b. Therefore, it is possible to simplify theoperation of replacing the output shaft part 46 a.

Furthermore, the tap holes 46 d, to which jigs such as the eyebolts 80are attachable, are provided on an upper surface of the carrier part 46b. Therefore, it is possible to increase the assemblability anddisassemblability of the planetary carrier 46. In the above-describedembodiment, the two tap holes 46 d are formed on the upper surface ofthe carrier part 46 b. Alternatively, three or more tap holes may beformed. In this case, a single bar-shaped member is passed through therings of the two eyebolts 80 attached to two of the three or more tapholes.

Furthermore, the carrier part 46 b is fastened to the output shaft part46 a using the three bolts 46 c serving as fastening members.Embodiments of the present invention, however, are not limited to thisconfiguration. For example, the carrier part 46 b may alternatively befastened to the output shaft part 46 a using one, two, or four or morefastening members.

Furthermore, in the above-described embodiment, the bolts 46 c areinserted into bolt holes that extend through the carrier part 46 b inits axial directions and are screwed into tap holes formed on the uppersurface of the disk portion 46 a 1 of the output shaft part 46 a.Embodiments of the present invention, however, are not limited to thisconfiguration. For example, the bolts 46 c may alternatively be insertedinto bolt holes extending through the disk portion 46 a 1 in its axialdirections and be screwed into tap holes formed on a lower surface ofthe carrier part 46 b. In this case, the tap holes 46 d, which areformed on the upper surface of the carrier part 46 b, may be formed on alower surface of the disk portion 46 a 1.

Next, a description is given, with reference to FIG. 9, of the dischargeof lubricant oil in the turning drive unit 40. FIG. 9 is an enlargedview of a region IX enclosed by a broken line in FIG. 6.

Referring to FIG. 9, the second gear case 52 includes a recess 52 r in apart that forms a bottom surface of the space SP1 in which the lubricantoil LB1 is present. In a plan view, the recess 52 r forms an annulargroove. In this embodiment, the recess 52 r is formed vertically belowthe disk holding portion 46 a 1 p, which is at the outer radial end ofthe disk portion 46 a 1 of the output shaft part 46 a of the planetarycarrier 46. Furthermore, the recess 52 r has such a depth and a width(radial length) as to be able to receive a lower end of the disk holdingportion 46 a 1 p, projecting vertically downward relative to other partsof the disk portion 46 a 1. Embodiments of the present invention,however, are not limited to this configuration. For example, the recess52 r may have a width smaller than the width of the disk holding portion46 a 1 p. In this case, the recess 52 r does not receive the lower endof the disk holding portion 46 a 1 p. Furthermore, the recess mayalternatively be formed at a position closer to or more distant from theaxis of rotation of the planetary carrier 46 instead of being formedimmediately below the disk holding portion 46 a 1 p. Furthermore, thesecond gear case 52 may include the recess 52 r irrespective of whetherthe disk holding portion 46 a 1 p is projecting vertically downward ornot.

Furthermore, the second gear case 52 includes a discharge passage 52 bthat is open on an interior bottom surface or an interior wall surfaceof the recess 52 r. In this embodiment, the discharge passage 52 bconnects the space SP1 and a space outside the second gear case 52 whilesloping downward from the interior bottom surface of the recess 52 to anexterior surface of the second gear case 52. A plug is attached to anexterior surface-side end of the discharge passage 52 b so as to allowthe lubricant oil LB1 inside the SP1 to be discharged as required.

FIGS. 10A, 10B and 100 are cross-sectional views of part of the secondgear case 52, illustrating other configurations of the recess 52 r.Referring to FIG. 10A, a recess 52 r-1 includes an interior bottomsurface that slopes downward toward its widthwise (radial) center.Furthermore, a discharge passage 52 b-1 is open at the center of theinterior bottom surface of the recess 52 r-1. Referring to FIG. 10B, arecess 52 r-2 includes an interior bottom surface that slopes downwardtoward its widthwise (radial) outer side. Furthermore, a dischargepassage 52 b-2 is open at the interior bottom surface of the recess 52r-2 on its widthwise (radial) outer side. Referring to FIG. 10C, arecess 52 r-3 includes an interior bottom surface that slopes downwardtoward its widthwise (radial) inner side. Furthermore, a dischargepassage 52 b-3 is open at the interior bottom surface of the recess 52r-3 on its widthwise (radial) inner side.

Next, a description is given, with reference to FIG. 11, of effectsproduced by the recess 52 r. FIG. 11 illustrates cross-sectional viewsillustrating the positional relationship between the planetary carrier46 and the second gear case 52. In FIG. 11, a configuration without therecess 52 r and a configuration with the recess 52 r are juxtaposed onthe left side and the right side, respectively. Specifically, thecross-sectional views of FIG. 11 illustrate the positional relationshipamong the output shaft part 46 a of the planetary carrier 46, the secondgear case 52, the bearing 56, the oil seals 57, the brake disks 60, andthe brake plates 62.

Referring to the left-side configuration of FIG. 11, the output shaftpart 46 a includes the disk portion 46 a 1 including the disk portion 46a 1 whose disk holding portion 46 a 1 p has a thickness D1 that is thesame as the thickness of other parts of the disk portion 46 a 1.Furthermore, the second gear case 52 includes a bottom plate part 52 aof a thickness D2. The bottom plate part 52 a forms a bottom surface ofthe space SP1 and includes a support portion 52 ap at its inner radialend. The support portion 52 ap supports the bearing 56 and the oil seals57. Furthermore, a clearance of a thickness D3 is formed between a lowersurface of the disk portion 46 a 1 (the disk holding portion 46 a 1 p)and an upper surface of the bottom plate part 52 a.

On the other hand, referring to the right-side configuration of FIG. 11,the second gear case 52 includes the recess 52 r depressed downward inthe bottom plate part 52 a. This allows the disk holding portion 46 a 1p to project downward relative to other parts of the disk portion 46 a1, thereby increasing the thickness of the disk holding portion from thethickness D1 to a thickness D1E. As a result, a recess 46 a 1 rdepressed upward is formed in the disk portion 46 a 1 of the outputshaft part 46 a.

As the comparison of the left-side configuration and the right-sideconfiguration of FIG. 11 illustrates, forming the recess 52 r on theupper surface of the bottom plate part 52 a allows the first turningspeed reducer 24-1 to increase the thickness of the disk holding portion46 a 1 p by a distance D4. As a result, it is possible for the firstturning speed reducer 24-1 to increase the stiffness of the disk holdingportion 46 a 1 p and to increase the proof stress of the output shaftpart 46 a against a braking reaction force generated at the time ofbraking by a brake unit. Furthermore, it is possible for the firstturning speed reducer 24-1 to increase the number of brake disks 60attached to the disk holding portion 46 a 1 p. This makes it possible toincrease the holding torque of a brake unit. Accordingly, it is possibleto more stably maintain the upper-part turning body 3 in a state whereturning is stopped.

Next, a description is given, with reference to FIG. 12, of effectsproduced by the recess 46 a 1 r and the recess 52 r. Like FIG. 11, FIG.12 illustrates cross-sectional views illustrating the positionalrelationship between the planetary carrier 46 and the second gear case52. In FIG. 12, a configuration without the recess 52 r and aconfiguration with the recess 52 r are juxtaposed on the left side andthe right side, respectively.

Referring to the left-side configuration of FIG. 12, the output shaftpart 46 a includes the disk portion 46 a 1 including the disk portion 46a 1 whose disk holding portion 46 a 1 p has a thickness D1′ that is thesame as the thickness of other parts of the disk portion 46 a 1.Furthermore, the second gear case 52 includes the bottom plate part 52 aof the thickness D2. Furthermore, a clearance of the thickness D3 isformed between the lower surface of the disk portion 46 a 1 (the diskholding portion 46 a 1 p) and the upper surface of the bottom plate part52 a.

On the other hand, referring to the right-side configuration of FIG. 12,the output shaft part 46 a includes the recess 46 a 1 r depressed upwardin the disk portion 46 a 1, so that the thickness D1′ of the diskportion 46 a 1 is reduced to a thickness D1C where the recess 46 a 1 ris formed. As a result, the disk holding portion 46 a 1 p is projectingdownward relative to other parts of the disk portion 46 a 1.Furthermore, referring to the right-side configuration of FIG. 12, thesecond gear case 52 includes the recess 52 r depressed downward in thebottom plate part 52 a, so that the thickness D2 of the bottom platepart 52 a is reduced to a thickness D2C where the recess 52 r is formed.As a result, the support portion 52 ap is projecting upward relative toother parts of the bottom plate part 52 a.

As the comparison of the left-side configuration and the right-sideconfiguration of FIG. 12 illustrates, forming the recess 46 a 1 r on thelower surface of the disk portion 46 a 1 and forming the recess 52 r onthe upper surface of the bottom plate part 52 a make it possible for thefirst turning speed reducer 24-1 to reduce its vertical length by adistance D5. In this case, the first turning speed reducer 24-1 reducesthe thickness of neither the disk holding portion 46 a 1 p nor thesupport portion 52 ap. Thus, it is possible for the first turning speedreducer 24-1 to reduce its vertical length while maintaining thestiffness of the disk holding portion 46 a 1 p and the support portion52 ap.

According to the above-described configuration, the second gear case 52includes the recess 52 r in a part that forms a bottom surface of thespace SP1 and includes the discharge passage 52 b that connects therecess 52 r and an external space, thus allowing an efficient dischargeof the lubricant oil LB1 at the time of replacing the lubricant oil LB1.

Furthermore, it is possible for the second gear case 52 to efficientlydischarge wear debris generated in components in the first turning speedreducer 24-1, such as the sun gear 42, the planetary gears 44, theinternal gear 48, the brake disks 60 and the brake plates 62, togetherwith the lubricant oil LB1. As a result, it is possible to prevent weardebris from adversely affecting the performance of the turning speedreducer 24.

Furthermore, providing the second gear case 52 with the recess 52 rmakes it possible for the second gear case 52 to increase the thicknessof the disk holding portion 46 a 1 p of the disk portion 46 a 1 whilemaintaining the clearance between the second gear case 52 and the diskportion 46 a 1 of the output shaft part 46 a. As a result, it ispossible to increase the stiffness of the disk holding portion 46 a 1 pand to increase the proof stress of the output shaft part 46 a against abraking reaction force generated at the time of braking by a brake unit.

All examples and conditional language provided herein are intended forpedagogical purposes of aiding the reader in understanding the inventionand the concepts contributed by the inventors to further the art, andare not to be construed as limitations to such specifically recitedexamples and conditions, nor does the organization of such examples inthe specification relate to a showing of the superiority or inferiorityof the invention. Although one or more embodiments of the presentinvention have been described in detail, it should be understood thatthe various changes, substitutions, and alterations could be made heretowithout departing from the spirit and scope of the invention.

For example, according to the above-described embodiment, the recess 52r of the second gear case 52 forms a groove that is annular in a planview and may slope toward its center, outer side or inner side in aradial direction. Embodiments of the present invention, however, are notlimited to this configuration. For example, the recess 52 r may slope ina circumferential direction so that the position of the recess 52 r islowest at the opening of the discharge passage 52 b. Furthermore, thewidth (radial length) and the depth (axial length) of the recess 52 maynot be uniform in a circumferential direction. Furthermore, the recess52 does not have to be annular and may be arcuate. In this case, therecess 52 r may be formed by providing either one recess or multiplerecesses in a circumferential direction.

Furthermore, according to the above-described embodiment, the singledischarge passage 52 b is connected to the recess 52 r of the secondgear case 52. Embodiments of the present invention, however, are notlimited to this configuration. For example, multiple discharge passagesmay be connected to the recess 52 r.

What is claimed is:
 1. A shovel, comprising: a turning drive unit, theturning drive unit including a turning electric motor; a turning speedreducer configured to transmit a rotational driving force of the turningelectric motor to a turnable body; a brake unit configured to maintainthe turnable body in a state where turning of the turnable body isstopped; and a case forming a space in which the turning speed reducerand the brake unit are lubricated with lubricant oil and accommodated,wherein a recess is formed in a part of the case that forms a bottomsurface of the space.
 2. The shovel as claimed in claim 1, wherein thebrake unit includes a brake disk configured to rotate with an outputshaft of the turning speed reducer; and a brake plate attached to thecase and configured to be pressed against the brake disk, the outputshaft includes a radially extending disk portion, the disk portionincludes a disk holding portion at an outer radial end of the diskportion, wherein the brake disk is attached to the disk holding portion,and the recess is formed vertically below the disk holding portion. 3.The shovel as claimed in claim 2, wherein the disk holding portion ofthe disk portion has a thickness greater than a thickness of anotherpart of the disk portion positioned radially inside the disk holdingportion, and a lower end of the disk holding portion is positionedinside the recess.
 4. The shovel as claimed in claim 1, wherein adischarge opening that communicates with a discharge passage throughwhich the lubricant oil is discharged is formed in the recess.
 5. Theshovel as claimed in claim 4, wherein an internal bottom surface of therecess includes a slope toward the discharge opening.